The mechanisms by which oral streptococci interact with teeth, saliva, and with each other to form cariogenic dental plaque are under investigation. Significant differences have been observed in the aggregation and adsorption to hydroxylapatite (HA) surfaces of S. mutans serotypes b, c, and d cells with salivas obtained from humans, monkeys and rats. The different salivas all inhibited sucrose-mediated adherence to glass of each of the three cell types in a similar manner. A method using a HA coated glass rod has been developed to measure the substantiveness of potential cariostatic agents on a saliva pellicle formed on the hydroxylapatite; the effects of each test agent on growth, acid production and sucrose-mediated adherence of S. mutans have been determined. HA adsorption patterns in the presence of sucrose of S. mutans mutants defective in glucan synthesis did not correlate with their decreased sucrose-mediated adherence to glass surfaces. Interactions of LTA, hydroxylapatite, sucrose and oral streptococci suggest a role for LTA in bacterial colonization to teeth.